Abstract
The expression of P-glycoprotein (Pgp) on normal human lymphocytes, and its drug exclusion capacity, implies that Pgp might be involved in cytokine secretion. We used two-color flow cytometry to detect simultaneously Pgp expression and IL-2 accumulation in resting and mitogen-activated human lymphocytes. Among resting lymphocytes from five healthy donors less than 1% were Pgp+ as determined by reactivity with the anti-Pgp monoclonal antibody (mAb) 4E3. The percentage of Pgp+ lymphocytes increased to 3% after 24 hr of mitogenic stimulation that induced maximal production of cytoplasmic IL-2. The percentage of lymphocytes that coexpressed membrane Pgp and cytoplasmic IL-2 accounted for <10% of the total IL-2 producing lymphocytes. Finally, mitogen-induced cytoplasmic IL-2 accumulation was enhanced by stimulation in the presence of monensin but not the Pgp functional inhibitor verapamil. Because mAb 4E3 detected lower than expected numbers of Pgp+ lymphocytes, we compared the binding of mAbs MRK16 and 4E3 concomitant with doxorubicin (DOX)-uptake by K562 and R7 tumor cells and purified CD8+ lymphocytes. The MRK16 mAb was found to be sensitive but not very specific (30%). In contrast, the sensitivity of 4E3 was equivalent to MRK16 (98%) and was highly specific (98.5%). There was also a positive association between DOX efflux and the level of Pgp expression as detected by 4E3 but not MRK16. Thus, human T cells do not markedly up-regulate their expression of functional Pgp molecules as detected by mAb 4E3 following activation, suggesting that Pgp does not play a major role in IL-2 secretion by activated T cells.
Original language | English (US) |
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Pages (from-to) | 239-246 |
Number of pages | 8 |
Journal | Journal of Clinical Immunology |
Volume | 19 |
Issue number | 4 |
DOIs | |
State | Published - 1999 |
Keywords
- Cytokine secretion
- Multidrug resistance
ASJC Scopus subject areas
- Immunology and Allergy
- Immunology